/**
 * Copyright 2010 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 *
 */
package org.waveprotocol.wave.client.wavepanel.view.dom;

import com.google.common.base.Preconditions;
import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.Element;

import org.waveprotocol.wave.client.uibuilder.BuilderHelper.Component;

/**
 * Helper for implementations of DOM-based views. In particular, provides
 * implementations of {@link Object#hashCode()} and
 * {@link Object#equals(Object)}.
 *
 */
public final class DomViewHelper {

  private DomViewHelper() {
  }

  /**
   * Defines the equality of DOM-based views (determined solely by the equality
   * of HTML ids).
   *
   * @see Object#equals(Object)
   */
  public static boolean equals(DomView src, Object tgt) {
    if (src == tgt) {
      return true;
    } else if (!(tgt instanceof DomView)) {
      return false;
    } else {
      return src.getId().equals(((DomView) tgt).getId());
    }
  }

  /**
   * Defines the hash code of DOM-based views (determined solely by the hashcode
   * of the HTML id).
   *
   * @see Object#hashCode()
   */
  public static int hashCode(DomView src) {
    return 37 + src.getId().hashCode();
  }

  public static Element load(String baseId, Component c) {
    Element e = Document.get().getElementById(c.getDomId(baseId));
    if (e == null) {
      throw new RuntimeException("Component not found: " + c);
    }
    return e;
  }

  public static Element getBefore(Element container, Element ref) {
    Preconditions.checkArgument(ref == null || ref.getParentElement().equals(container));
    if (ref == null) {
      return getLastChildElement(container);
    } else {
      return getPreviousSiblingElement(ref);
    }
  }

  public static Element getAfter(Element container, Element ref) {
    Preconditions.checkArgument(ref == null || ref.getParentElement().equals(container));
    if (ref == null) {
      return container.getFirstChildElement();
    } else {
      return ref.getNextSiblingElement();
    }
  }

  public static void attachAfter(Element container, Element ref, Element target) {
    Preconditions.checkArgument(ref == null || ref.getParentElement().equals(container));
    Preconditions.checkArgument(target.getParentElement() == null);
    if (ref == null) {
      container.insertFirst(target);
    } else {
      container.insertAfter(target, ref);
    }
  }

  public static void attachBefore(Element container, Element ref, Element target) {
    Preconditions.checkArgument(ref == null || ref.getParentElement().equals(container));
    Preconditions.checkArgument(target.getParentElement() == null);
    if (ref == null) {
      container.appendChild(target);
    } else {
      container.insertBefore(target, ref);
    }
  }

  public static void detach(Element container, Element target) {
    Preconditions.checkArgument(target != null && target.getParentElement().equals(container));
    target.removeFromParent();
  }

  //
  // Helpers, making up for deficiencies in GWT's DOM API.
  //

  public static native Element getLastChildElement(Element elem) /*-{
    var child = elem.lastChild;
    while (child && child.nodeType != 1) {
      child = child.previousSibling;
    }
    return child;
  }-*/;

  public static native Element getPreviousSiblingElement(Element elem) /*-{
    var sib = elem.previousSibling;
    while (sib && sib.nodeType != 1) {
      sib = sib.previousSibling;
    }
    return sib;
  }-*/;
}